Tang Hall’s overnight guests policies follow that of MIT’s Residential Housing and Dining’s policies, which can be found here.
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For your convenience, we have reiterated it below:

A guest is someone (MIT or non-MIT affiliated) who does not live in your residence hall.

You are permitted to have guests in your residence, including the common areas of the residence hall, under the following conditions:

When you host guests, for an event or overnight, you are responsible for their conduct and any damage they might cause.

You may not have overnight guests for more than three nights in any given week. Some halls may have an overnight guest policy which may be more restrictive. It is the resident’s obligation to check with the House Team (Housemasters or House Manager) to determine if specific policies exist and to abide by all applicable policies.

You must obtain, in advance, the permission of all students of the room/suite in which the overnight guest is visiting or staying. Consideration should be given to the rights and reasonable expectations of your roommate(s) at all times.

Sleeping overnight in the public common areas of a residence (e.g., lounges) is prohibited.